Life cycle carbon and cost assessment comparing milled and whole timber truss systems and insulation options for affordable housing

Abstract

Increasing demand for housing is one of the biggest challenges facing the world. Affordable housing is a key priority of the UK government in addressing this challenge, which calls for innovative construction methods to address the issue of fuel poverty at an affordable cost. Timber-based modern methods of construction are one of the key solutions to resolve the existing housing crisis while managing climate change. Therefore, this paper presents a case study of “Integra House”, which is a proof of concept of a novel truss technology. The case study is an affordable housing prototype that performs well in both life cycle carbon and cost. The proposed construction uses a novel timber truss technology which makes up the floor, walls and roof of the house, thereby reducing on-site operations and waste while providing a low-carbon low-cost design. The prototype underwent design optimisation and evaluation of options; workshop-based production and performance evaluation of elemental prototypes; production and performance evaluation of a full-scale dwelling prototype; and comparison of capital and life cycle costs and environmental impacts. Further, it underwent a simulation-based optimisation to maximize its performance in cost and carbon by replacing milled timber trusses with whole timber trusses and Rockwool insulation with wood wool insulation. The optimised design option (whole timber) has an EC of 261kgCO2per m2 and costs £682 per m2 (excludes substructure, services and fitout) and its operational carbon is 7.9 kgCO2 per m2/annum and costs £3.30 per m2/annum to operate. Life cycle costs and carbon comparison of the two design prototypes concluded that the whole timber design outperformed the milled timber design in both cost and carbon aspects, by 23% and 30% respectively due to being extremely inexpensive and requiring minimal processing compared to the milled timber option.